Sorry for the late reply - was offline last week!

On Sat, 13 Oct 2001, Roman Weissgaerber wrote:

> If there is just one interface and no alternative interface then
> the USB spec says that a device can stall (-EPIPE) on the 
> usb_set_interface() request. So there seems nothing wrong here.

Ah - thanks! Didn't remember that. So it is ok from usb spec. The IrDA USB
class spec. v1.0, section 6.1.10 however requires the device, when
configured, shall support Set Interface standard request for IF 0, AS 0.
I'm not going to argue whether returning protocol-stall could be 
considered some way of support, but the following sentence requiring the
device shall STALL on any _other_ Set Interface request suggests to me
this is not what was meant.
I'd say it's just another device misbehavior - but one we can easily live
with. In fact the irda-usb does already ignore the EPIPE.

> The error code sharing of stall and babble errors (both -EPIPE)
> is a design error of the URB interface and should be resolved 
> immediately. STALLs are part of the protocol and BABBLE 
> is a real error.
> 
> [...]
> 
> Do you really get a BABBLE error or just a STALL. 
> I would guess it is a STALL first.

I've just verified this with UHCI and Davids uhci-1015 patch applied:
Yes, it is the device returning STALL - no BABBLE detected!
So my speculation is obsolete and I think I can't provide any more
information on this issue, because I can not reproduce it on UP with
Intel-UHCI.

Martin


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